Dengue II virus when inoculated intraamniotically into pregnant rhesus monkeys (Macaca mulatta) was found to be a teratogen in this species. Epidemics of Dengue fever are frequent in certain human populations. The possible teratogenic effects of this virus in humans should be investigated. Venezuelan Equine Encephalitis (VEE) has been implicated as a human teratogen. We are studying the pathogenesis of this infection in pregnant rhesus monkeys. The virus produced hydrocephalus 100% when inoculated intracerebrally into the fetus. We are developing a rhesus monkey cytomegalovirus model. This virus produces CNS lesions in the fetus when inoculated intraamniotically into CMV antibody positive pregnant rhesus monkeys.